Interesting script... let's test it...
Canon A570IS on AUTO,
1. Auto High ISO, shot taken at ISO 800
2. Auto High ISO, script shot at ISO 800 - barely a difference
3. Auto ISO, shot taken at ISO 200
4. Auto ISO, script shot at ISO 200, longer exposure, looks nice and sharp.
The pictures have the original EXIF. It is a better way to get what you see in terms of metering, but the exposure time will kill you. Don't expect this to work in hand free or moving objects scenes. I go manual usually, so I won't really use this script, great job anyway!
Tested when using the flash, it increases the exposure time from 1/60 to 0.6 and lowers the flash output. Nice color range, might change my mind about it...